sodium bicarbonate
in review
5 min read
Updated 2026-09-03
sodium bicarbonate
- Proven indications: NAGMA replacement, urinary alkalinisation (salicylate/methotrexate toxicity), Na⁺-channel blockade reversal (TCA overdose)
- Severe ICU acidaemia (pH ≤ 7.20): may reduce RRT need; mortality benefit uncertain outside pH ≤ 7.10
- No role: lactic acidosis at pH ≥ 7.15, undifferentiated cardiac arrest
mechanism
- H⁺ + HCO₃⁻ ⇌ H₂CO₃ ⇌ H₂O + CO₂ — open-system dependent: pH correction requires the lungs to clear generated CO₂. Fixed ventilation or hypercapnic respiratory failure → risk of paradoxical intracellular and CSF acidosis from CO₂ accumulation
- Isotonic bicarbonate (150 mmol/L Na⁺, 150 mmol/L HCO₃⁻) has effective strong ion difference +150 → expands intravascular volume, corrects hyperchloraemic NAGMA
- Na⁺-channel blockade reversal (TCA) — ↑ extracellular Na⁺ overcomes competitive channel block; alkalaemia favours un-ionised (lower-affinity) drug form and independently ↑ Na⁺ channel conductance
- Distal Na⁺ delivery with non-reabsorbable HCO₃⁻ → ENaC activation → lumen-negative gradient → kaliuresis via ROMK/BK channels (useful in hyperkalaemic prerenal acute kidney injury)
indications
| evidence | indication | route | notes |
|---|---|---|---|
| proven | NAGMA (GI or renal HCO₃⁻ losses) | oral / IV | replaces ongoing losses — diarrhoea, fistulae, RTA types 1 & 2 |
| proven | urinary alkalinisation (salicylates, methotrexate) | IV isotonic | target urine pH 7.5–8.0; keep arterial pH ≤ 7.55 |
| proven | Na⁺-channel blockade (TCA) | IV hypertonic (8.4%) | ↑ extracellular Na⁺ + alkalaemia overcomes fast-channel blockade → titrate to QRS narrowing. Ceilings: Na⁺ ≤ 155 mmol/L, pH ≤ 7.55 |
| suggested, unproven — KDIGO 2024, BiCARB 2020 | CKD G3–G5 metabolic acidosis | oral | no graded KDIGO recommendation. 15-trial meta-analysis: no significant effect on kidney failure (HR 0.81; 0.54–1.22). BiCARB: no functional/renal benefit. Frame as preventing HCO₃⁻ < 18 mmol/L, not targeting ≥ 22 |
| contested — SSC 2026, SODa-BIC, IPD meta-analysis | severe acidaemia pH ≤ 7.20 | IV isotonic | SSC 2026: conditional for at pH ≤ 7.20 + AKIN 2–3 (pre-dates SODa-BIC); suggests against at pH ≥ 7.15 for haemodynamics. BICAR-ICU AKIN 2–3 signal not replicated by SODa-BIC. IPD meta-analysis: ↓ RRT (NNT ~6); mortality signal only at pH ≤ 7.10 — hypothesis-generating (trial-sequential analysis formally inconclusive) |
| against | undifferentiated cardiac arrest | IV | no improvement in ROSC or survival. Exception: suspected hyperkalaemia-associated arrest (AHA/ILCOR algorithms) |
| against — Umpierrez 2024 | DKA (unless pH < 7.0) | IV | pH < 7.0 (previously 6.9). Concerns: delayed ketone clearance, paradoxical CSF acidosis, hypokalaemia. Paediatric cerebral oedema association |
dosing
oral (chronic)
| formulation | dose | notes |
|---|---|---|
| NaHCO₃ tablets 650 mg (7.7 mmol) | 650 mg PO 2–3×/day | titrate every 2–4 weeks |
| sodium citrate/citric acid (Shohl’s solution) | 1 mmol/mL alkali equivalent | useful if tablets cause CO₂ bloating |
- Target: avoid HCO₃⁻ < 18 mmol/L; do not overcorrect above upper limit of normal
- BASE pilot dosing framework: 0.5–0.8 mmol/kg lean body weight/day
oral bicarb in salicylate toxicity
Contraindicated — raising gastric pH accelerates tablet dissolution and absorption. Use IV alkalinisation only.
intravenous (acute)
| setting | recipe | rate / dose |
|---|---|---|
| isotonic infusion (acidaemia, AKI) | 150 mL 8.4% NaHCO₃ (3 × 50 mL ampoules = 150 mmol) in 850 mL sterile water or D5W → 150 mmol/L Na⁺, ~300 mOsm/L | 100–200 mL/hr, titrate to pH 7.25–7.30 or HCO₃⁻ ≈ 18–20 mmol/L (correction endpoint, not an efficacy threshold) |
| hypertonic bolus (TCA, severe Na⁺-channel blockade) | 1–2 ampoules 8.4% (50–100 mmol) | IV push over 1–2 min |
| urinary alkalinisation (salicylate) | ~1 mmol/kg bolus, then 3 ampoules in 1 L D5W ± 40 mmol KCl | titrate to urine pH > 7.5; alkalinise even when respiratory alkalosis predominates |
key points
- Ventilation is non-negotiable — if the patient cannot blow off CO₂ (intubated with fixed minute ventilation, severe COPD), infused bicarb worsens intracellular acidosis without correcting pH
- Each litre of isotonic bicarb delivers 150 mmol Na⁺ — volume and sodium load matters in oliguric AKI or decompensated heart failure
- Repleting K⁺ and iCa²⁺ alongside bicarb is mandatory — alkalaemia shifts K⁺ intracellularly and increases Ca²⁺-albumin binding
- The CKD evidence is weaker than often stated: KDIGO 2024 gives no graded recommendation, and the largest trial (BiCARB 2020) was negative. Veverimer (non-absorbed HCl binder) is an investigational alternative
overshoot alkalosis
Rapid correction → leftward shift of oxyhaemoglobin dissociation curve (↑ Hb-O₂ affinity, ↓ tissue O₂ unloading), tetany, seizures. Worsens intracellular/CSF acidosis if CO₂ clearance is limited.
adverse effects
- Hypokalaemia — intracellular H⁺/K⁺ shift + kaliuresis; replete aggressively (including during TCA alkalaemia therapy)
- Ionised hypocalcaemia — alkalaemia ↑ Ca²⁺-albumin binding → ↓ iCa²⁺, ↓ contractility
- Na⁺ and volume overload — pulmonary oedema risk in oliguria or heart failure
- Overshoot metabolic alkalosis — see above
evidence
- BICAR-ICU (2018) — n=389, severe metabolic acidaemia in ICU. Primary composite negative (day-28 death + organ failure: 71% vs 66%, p=0.24). Prespecified AKIN 2–3 subgroup: ↓ mortality (p=0.028) and ↓ RRT — hypothesis-generating only
- SODa-BIC (2026) — no reduction in major adverse kidney events, mortality, or RRT in acidaemic shock; null across all prespecified subgroups including severe acidosis and advanced AKI
- BICAR-ICU2 + IPD meta-analysis (2026) — n=1,016. No overall 90-day mortality benefit (RR 0.96). ↓ RRT (34.8% vs 50.7%; RR 0.69, NNT ~6 — whether this reflects true renal benefit versus deferred/avoided dialysis in transiently acidaemic patients is unsettled). Mortality interaction at pH ≤ 7.10 (p=0.006) but overall result null and a parallel 4-trial meta-analysis (n=1,111; Chen, Crit Care Med. 2026) found this signal formally inconclusive on trial-sequential analysis — hypothesis-generating, not an actionable threshold. No significant interaction by AKI status (p=0.11) — proposed effect modifier is depth of acidaemia rather than AKI stage
- BiCARB (2020) — oral bicarb in older adults with CKD G3–G4: no benefit on renal function or physical function
- BASE pilot (2020) — dosing and safety of oral bicarb in CKD (0.5 vs 0.8 mmol/kg/day)